1. Technical Field
This disclosure generally relates to liquid jet heads and image forming apparatuses.
2. Description of the Related Art
Generally, as an image forming apparatus such as a printer, facsimile, copier, plotter, or a multiple function processing machine including the printer, facsimile, copier, and the plotter, the following apparatus is known. In the apparatus, while a recording medium is conveyed, a liquid drop of recording liquid (hereinafter “ink”) is adhered to the recording medium by using a liquid jet device including a recording head formed of a liquid jet head configured to jet the liquid drop of the recording liquid, so that image forming such as recording or printing is performed.
Hereinafter, the recording medium is called a sheet, a paper, a recording paper, or a transfer material. However, there is no limitation of material for the paper or the transfer material. The meanings of image forming include recording, printing, and others.
The image forming apparatus means an apparatus configured to jet liquid onto a medium such as a paper, thread, fiber, leather, hides, metal, plastic, glass, wood, or ceramic so that images are formed. “Image forming” means not only providing an image of characters, figures, or the like on the medium but also providing an image such as a pattern having no meanings on the medium. In addition, the liquid is not limited to the recording liquid or the ink and any liquid that is a fluid when being jetted can be applied to the liquid. Furthermore, the liquid jet device means a device configured to jet the liquid from the liquid jet head and is not limited to the device for image forming.
As a pressure generating part (actuator part) of the liquid jet head configured to generate pressure for pressurizing the ink that is a liquid in a individual flow path (hereinafter “pressurizing liquid room”), a piezo-electric actuator formed of a piezo-electric element or the like, a thermal actuator formed by a heat element or the like, an electrostatic actuator for generating an electrostatic force, and others are known.
In the meantime, in the liquid jet head, if an air bubble remains in a flow path when liquid flows, a liquid drop cannot be jetted from the nozzle (nozzle down) or bad jetting such that a jetting misdirection of the liquid drop may occur. Accordingly, it is desired to improve air bubble discharging properties. Because of this, a head is known where a hydrophilic or water-repellent surface treatment is applied to an inner wall surface of the flow path.
For example, Japanese Laid-Open Patent Application Publication No. 61-141565 describes that an inner wall surface of a nozzle is treated so as to be hydrophilic.
Japanese Laid-Open Patent Application Publication No. 2001-179996 describes that a water-repellent surface treatment is applied to a part coming in contact with an ink of an ink jet printer head main body.
Japanese Patent Publication No. 3173187 describes an ink jet head including ink flow path and nozzle holes arranged in contact with the flow paths for discharging ink in such a manner that the flow paths are formed partly or entirely of a piezo-electric material, wherein an insulation layer is formed on a surface coming in contact with the ink of the flow paths and the insulation layer of the flow paths is covered with a hydrophilic film made of alumina or zirconia.
Japanese Laid-Open Patent Application Publication No. 2001-195599 describes a head where a face surface that is an external surface of a member forming an orifice for jetting a liquid drop is coated with a material having ultra-hydrophilicity. Japanese Laid-Open Patent Application Publication No. 11-198377 describes a head where an inorganic hydrophilic film having a photocatalitic function is directly formed on inner walls of all ink flow paths from an inner wall of a common liquid chamber of a ceiling member to a jetting outlet.
Japanese Laid-Open Patent Application Publication No. 63-122551 describes a head where a first substrate forming a wall-shaped member limiting an ink flow path and a second substrate limiting an upper surface of the ink flow path and a discharge outlet by an adhesive layer whose wettability for ink is equal to or greater than that of the second substrate.
Japanese Laid-Open Patent Application Publication No. 11-58745 describes a head wherein a nozzle is formed by applying plasma dry etching from a pressurized room side to a resin molding nozzle forming member.
Japanese Laid-Open Patent Application Publication No. 5-155015 describes a head having a flow path plate having an ink cavity and a piezoelectric element filled with a filler of elastic material in a groove, many of which grooves divide a driving piezoelectric element which corresponds to the ink cavity, and are separated through a thin film member having a low coefficient of water absorption.
However, for example, in the head discussed in Japanese Patent Publication No. 3173187, the insulation layer is formed on the surface coming in contact with the ink of the flow paths and the insulation layer of the flow path is covered with a hydrophilic film made of alumina or zirconia. More specifically, the insulation film is formed by applying a thermal decomposition CVD method to an organic insulation layer.
Accordingly, a film thickness or a film thickness distribution is generated inside the flow path. In addition, a thermal treatment is applied by circulating liquid where alumina sol or zirconium sol is diluted as a hydrophilic film on such an organic insulation film surface so as to coat the film surface.
Therefore, due to the influence of the film thickness or a film thickness distribution of the base organic insulation film, the hydrophilic properties are varied so that even air bubble properties cannot be achieved.
On the other hand, as described in Japanese Laid-Open Patent Application Publication No. 61-141565, Japanese Laid-Open Patent Application Publication No. 2001-179996, Japanese Laid-Open Patent Application Publication No. 2001-195599, Japanese Laid-Open Patent Application Publication No. 11-198377, and Japanese Laid-Open Patent Application Publication No. 11-58745, since the hydrophilic treatment film or water-repellent treatment film is formed on the internal wall surface of the flow path, unevenness of the hydrophilicity or water-repellency may be generated due to influence of a material of a member forming the flow path. In addition, in the case where the water-repellent treatment is applied to the internal wall surface of the flow path, the ability to discharge air bubbles is bad.
In the meantime, in the image forming apparatus, it is required to output a higher quality image at a higher printing speed. Especially, for improvement of the printing speed, the head is made long. A full line type head which can cover the entire width of the medium is about to be realized.
In a long head such as a line type head, the size of a flow path member forming an individual liquid room becomes large. Accordingly, in a case where a complex flow path configuration is formed at low cost, it is preferable to apply a stacked structure such as double layer structure of a metal member such as SUS rather than an expensive member such as silicon.
In this case, while the flow path member is formed by connecting plural metal members by an adhesive. If wetting ability is a concern, an adhesive such as epoxy resin having low hydrophilicity is used. However, if the hydrophilicity of a part of the inner wall surface of the individual flow path is low, as discussed above, the air bubble discharge-ability becomes bad.